1) A group of more-or-less anonymous people who are pretty much the only line of defense for this site to prevent it from being totally abused. They are pretty much the only thing between you and about 50 million explicit, pornographic, abusive, misogynistic, racist, or just plain stupid entries.
Editors have specific guidelines they must follow. However, these are often vague (especially if it's hard to tell, for example, if a term is just explaining a racial slur, or if it is in fact racist).
If your definition doesn't get published, it could be for one of two reasons:
A) It wasn't that good or
B) Someone just didn't like it for some reason.

In that case, try again...
However, bitching about them probably won't help.

1. The maintainance crew/demi-gods of Urban Dictionary.
2. A group of Urban Dictionary users whose goal in life is to spread new colloquialisms, lingos, and jargon to the youth of today.
3. The people who reject other people's definitions, then publish the angry slurs against the editors just to spite the poor sods.

Why the fuck did the Urban Dictionary editors reject my definition when I know that my best friend's screenname is not an acceptable entry?

a load of wankers that always choose not to publish your entries for some unknown reason. probably due to the fact that they are american and dont understand irish humour. or they are crap at geography.